1. Field of the Invention
This invention relates to a new process for preparing aromatic hydrocarbon polymers.
More specifically, it relates to a process for preparing polyarylenes by the catalytic oxidative polymerization of arenes and combinations of different arenes.
2. The Prior Art
It is known that polyarylenes in general, and poly(p-phenylene) in particular, have excellent resistance to thermal, oxidative, and radiative degradation, and these characteristics are reflected in their utility as solid lubricants, lubricant additives, insulators, pigments, ablative materials, oxidation inhibitors, stabilizers against heat and light, and laminate binders for heat shields.
Larson & Moore, Inorg. Chem. 5, 801 (1966) disclose the reaction of refluxing benzene with MoOCl.sub.4 to give poly(p-phenylene). The reaction is stoichiometric, not catalytic, the yield is 40% based on MoOCl.sub.4, and the product is contaminated with significant amounts of chlorine (4.46%) and molybdenum (3.64%).
Omae & Hirabashi, Jap. Pat. No. 2,280/67, published Feb. 1, 1967, disclose the reaction of benzene with oxygen in the presence of molybdenum pentachloride and boron trifluoride at 80.degree. C. in an autoclave to give a brown polymer. Although the MoCl.sub.5 is said to be a catalyst, 81.9 g of MoCl.sub.5 is used with 156 g of benzene, and the yield of polymer (assumed to be poly(p-phenylene)) is only 46% based on MoCl.sub.5 as a stoichiometric oxidant. Furthermore, only 0.0035 g of polymer per mmol of Mo is obtained.
Shepard & Dannels U.S. Pat. No. 3,386,899 (1968) disclose the polymerization of benzene and polycyclic aromatic hydrocarbons by anodic oxidation in liquid hydrogen fluoride. Molybdenum anodes are disclosed. Benzene is the monomer in most of the examples, and the highest yield of polymer therefrom is 36%. Conversion of o-terphenyl to a solid polymer in 22% yield is disclosed, but the products from naphthalene and biphenyl are described as "viscous condensation products".
U.S. Pat. No. 3,547,790 is a division of the foregoing patent.
Weichman & Walsh U.S. Pat. No. 3,480,568 (1969) disclose the conversion of benzene to poly(p-phenylene) by oxygen in the presence of a CuCl.sub.2 /AlCl.sub.3 catalyst. The maximum catalytic yield is only 197.5%, i.e., slightly less than twice the theoretical amount of polymer obtainable with CuCl.sub.2 as a stoichiometric oxidant. The yield of polymer can also be expressed as 0.075 g per mmol of Cu.
Frevel et al. U.S. Pat. No. 3,494,877 (1970) disclose a process for polymerizing aromatic hydrocarbons such as benzene, biphenyl, and naphthalene by reaction with oxygen in the presence of a palladium catalyst, aqueous sulfuric acid, and a large excess of a metal sulfate capable of oxidizing Pd(0) to Pd(2). Sulfates of iron and vanadium are disclosed as oxidants. The products, however, appear to be low in molecular weight.
Bilow & Rust U.S. Pat. No. 3,565,832 (1971) disclose the conversion of aromatic hydrocarbons, including mixtures of hydrocarbons, to polymers by reaction with oxygen in the presence of Lewis-acid catalysts such as BF.sub.3, FeCl.sub.3, TaCl.sub.5, ZrCl.sub.4. In addition, it is disclosed that an oxidant such as cupric chloride, silver oxide, or vanadium pentoxide can be used with the Lewis acid. There is no disclosure of molybdenum compounds as catalysts or oxidants.
Related patents issued to Bilow et al. and containing essentially the same disclosures include the following:
U.S. Pat. Nos. 3,578,611; 3,582,498; 3,595,811; 3,677,976; 3,678,006;
Yoshimoto and Itatani, Bull. Chem. Soc. Jap. 46 (8), 2490 (1973), disclose reaction of naphthalene with 1:1 nitrogen:oxygen in the presence of palladium acetate and acetylacetone at 150.degree. C. for four hours to give a mixture of isomeric binaphthyls. The nitrogen:oxygen mixture was introduced at 50 kg/cm.sup.2 at room temperature, so the starting partial pressure of oxygen at 150.degree. C. was at least 345 psi. There is no disclosure of polymer formation. Other aromatic compounds gave similar coupling reactions.
Kovacic and Lange, J. Org. Chem. 28 968 (1963), disclose reaction of benzene with molybdenum pentachloride in the presence of water or titanium tetrachloride as cocatalyst to give "p-polyphenyl" (poly(p-phenylene)). The reaction is stoichiometric, not catalytic. When water was the cocatalyst, the yields were about 6-13% and the products contained 2.7-9% Cl. When TiCl.sub.4 was the cocatalyst, the yields were 17-28% and the products contained 10-20% Cl.
Kovacic and Oziomek, Macromolecular Syntheses 2, 23 (1966), disclose polymerization of benzene to poly(p-phenylene) in the presence of aluminum chloride and cupric chloride. To date all these methods have suffered from one or more of the following disadvantages:
a. They consume electric power, which is in great demand and short supply.
b. They consume large amounts of chemical oxidants; the reduction products of these oxidants must be removed from the polymer and reclaimed and/or discarded.
c. They give polymers containing metallic residues that may be toxic or deleterious to the properties of the polymer.
d. They require recovery of precious-metal catalysts.
e. They are inefficient in terms of moles of carbon-carbon bonds formed per mole of catalyst.
f. In some instances only low molecular weight products are obtained.